Modified filler composition and papermaking process using the same

ABSTRACT

A modified filler composition used in papermaking is provided. The modified filler composition contains microfibrillated cellulose, filler, and latex having a glass transition temperature of less than 20° C. The dry weight of the microfibrillated cellulose is about 0.1% to about 10% that of the filler; the dry weight of the latex is about 0.1% to about 15% that of the filler.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to People's Republic ofChina Patent Application No. 201310045150.X, filed Feb. 5, 2013, whichis hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a modified filler composition used inthe field of papermaking, and a papermaking process using the modifiedfiller composition.

2. Description of Related Art

Microfibrillated cellulose is cellulose microfibrils defibrillated fromcellulosic materials by mechanical methods and/or the TEMPO catalyticoxidation method. The microfibrillated cellulose contains water-solublecellulose and water-insoluble cellulose. The microfibrillated cellulosehas dimensions of about 100 nm to about several millimeters in length,and about 3 nm to tens of micrometers in diameter. Due to a large numberof carboxyl groups of the microfibrillated cellulose, high aspect ratio,and good flexibility, the microfibrillated cellulose made by the TEMPOcatalytic oxidation method is generally added into paper pulp to improvethe strength properties of the paper made using the same.

In the field of papermaking, adding filler to the paper pulp caneffectively lower down the cost. However, if both filler andmicrofibrillated cellulose were added into the paper pulp, the fillerwould inhibit the hydrogen bonding of the microfibrillated cellulose. Inaddition, the negatively charged microfibrillated cellulose would repelthe negatively charged or neutral filler, causing the finer fillerparticles to easily aggregate. Therefore, adding both filler andmicrofibrillated cellulose to the paper pulp leads to a non-uniformdistribution of filler particles on the microfibrillated cellulose, thusdecreasing the filler retention.

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE FIGURE

Many aspects of the disclosure can be better understood with referenceto the following drawing. The components in the drawing are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the disclosure.

FIG. 1 is a scanning electron micrograph of a modified fillercomposition of Example 1.

FIG. 2 is a scanning electron micrograph of a filler composition ofComparative Example 1.

DETAILED DESCRIPTION

The microfibrillated cellulose used in this disclosure is made by theTEMPO catalytic oxidation method.

One example for preparing the microfibrillated cellulose by the TEMPOcatalytic oxidation method may include the following steps: (1)providing bleached kraft pulp (BKP) and beating the pulp; (2) providingthe beaten pulp having an amount by dry weight of 100 parts, andadjusting the concentration of the beaten pulp to about 2%; (3) adding acatalyst having an amount by dry weight of about 0.001 part to about 1part to the above pulp, the catalyst being TEMPO((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) or a derivative of TEMPO; (4)adding an assistant catalyst having an amount by dry weight of about0.01 part to about 10 parts into the pulp, the assistant catalystconsisting of iodides, bromides, borates, or a mixture thereof; (4)adding an oxidant (sodium hypochlorite) having an amount by dry weightof about 0.1 part to about 20 parts into the pulp and stirring, keepingthe pH value of the pulp to be in a range from about 9.5 to about 11;(5) the pulp and the oxidant reacting for about 0.5 hours to 4 hours toobtain a mixture containing oxidized celluloses, TEMPO, catalyst, andwater; (6) removing the residual catalyst and TEMPO from the mixture;(7) mechanically treating the oxidized celluloses by ultrasonication orhigh-pressure homogenization.

During the reaction process of the cellulose and the oxidant, somehydroxyl groups (—OH) on the chains of glucose of the cellulose areselectively oxidized to carboxyl groups (—COOH), which have strongernegative charges than the hydroxyl groups. Thus, the oxidized cellulosemolecules easily delaminate and defibrillate cellulose microfibrils dueto the strong electrostatic repulsion in the cellulose molecules.

The microfibrillated cellulose made by the TEMPO catalytic oxidationmethod has strong negative charge due to the carboxyl groups. Thecontent of the carboxyl groups of the microfibrillated cellulose is inthe range from about 0.06 to about 1.7 mmol/g. The microfibrillatedcellulose has a complex composition, which substantially contains bothwater-soluble cellulose and water-insoluble cellulose. The water-solublecellulose further contains nanocrystalline cellulose (NCC),nanofibrillated cellulose (NFC), and oligosaccharides, for example. Thewater-soluble cellulose (such as NFC) may position on the cell wall ofthe water-insoluble cellulose.

The modified filler composition in this disclosure containsmicrofibrillated cellulose and latex, wherein the dry weight of themicrofibrillated cellulose in the modified filler composition is about0.1% to about 10% that of the filler, and the dry weight of the latex inthe modified filler composition is about 0.1% to about 15% that of thefiller. The modified filler composition may further contain water.

The microfibrillated cellulose in the modified filler composition ismade by the TEMPO catalytic oxidation method. The content of carboxylgroups of the microfibrillated cellulose is in the range from about 0.06to about 1.7 mmol/g. The microfibrillated cellulose containswater-soluble cellulose having a mass percentage of 0.1% to 50% andwater-insoluble cellulose having a mass percentage of 10% to 99.9%.

The filler is composed of ground calcium carbonate (GCC), precipitatedcalcium carbonate (PCC), kaolin, talc, or any combination thereof. Inthis embodiment, more than 50% of the filler has a particle diameterless than or equal to 2 μm.

The latex has a glass transition temperature (T_(g)) of less than 20° C.In one embodiment, the T_(g) of the latex is less than 10° C. The latexis an emulsion, and the latex is consisted of polybutadiene latex,styrene-butadiene latex, carboxylic butadiene-styrene latex, cationicbutadiene-styrene latex, polyvinyl acetate latex, or any combinationthereof.

The latex in the modified filler composition makes the filler particlesdistribute uniformly on the surface of the microfibrillated cellulose. Apossible mechanism for this is illustrated as following: (1) the ambienttemperature of the modified filler composition is higher than the T_(g)of the latex, so the latex becomes unstable and demulsifies; (2) thefiller particles have a large specific surface area, so easily adsorbthe demulsified latex; (3) thus, carbon-carbon double bonds (—[C═C]—) oflatex distribute on surfaces of the filler particles. Carbon-carbondouble bonds easily react with microfibrillated cellulose. Therefore,the latex is equivalent to a binder or a media for coupling themicrofibrillated cellulose and the filler together.

The modified filler composition may further contain a cross-linkingagent. The cross-linking agent is a borate cross-linking agent, a boraxcross-linking agent, or dialdehyde cross-linking agent (such asoxaldehyde or glutaric dialdehyde). The dry weight of the cross-linkingagent is about 0.1% to about 15% that of the latex. The cross-linkingagent promotes the cross-linking between the latex and themicrofibrillated cellulose to form a network structure, which isbeneficial for increasing the filler retention on the microfibrillatedcellulose.

The modified filler composition can be made by directly mixing thefiller, the microfibrillated cellulose, and the latex together. Duringthe mixing process, the temperature of the composition is maintained ina range from 20° C. to 110° C. In this embodiment, the temperature ofthe composition is kept in a range from 20° C. to 70° C. In otherembodiments, the temperature of the composition is kept in a range from30° C. to 50° C.

One example for preparing the modified filler composition may includethe following steps: (1) providing a filler suspension; (2) adding themicrofibrillated cellulose into the filler suspension to obtain amixture, the dry weight of the microfibrillated cellulose being about0.1% to about 10% that of the filler; (3) adding the latex into theabove mixture, the dry weight of the latex being about 0.1% to about 15%that of the filler; (4) stirring the mixture with a speed of about 800revolutions per minute (RPM) for about 5 min between about 20° C. toabout 110° C.

The filler adsorbing on the surface of the microfibrillated cellulosehas a particle size uniformity of less than 10. The particle sizeuniformity is calculated by dividing the standard deviation of theparticle diameter by the mean particle size.

A papermaking process using the above modified filler compositionincludes the following steps.

Step 1: providing a paper pulp.

Step 2: adding the above modified filler composition into the paperpulp, and selectively adding or not adding unmodified filler to thepaper pulp.

Thus, the filler in the paper pulp is either all from the modifiedfiller composition, or is a combination of the modified fillercomposition and the unmodified filler. The total weight of the filleradded into the paper pulp is 10% to 300% of the dry weight of the pulpfiber. The weight of filler from the modified filler composition is 80%to 100% of the total weight of the filler in the paper pulp. Themicrofibrillated cellulose from the modified filler composition is aportion of the pulp fiber.

Step 3: adding at least one auxiliary additive into the paper pulp.

The auxiliary additive may contain starch, retention aids, or the like.The starch is consisted of anionic starch, oxidized starch, graftedstarch, amphoteric starch, or any combination thereof. The retentionaids are either one-component retention aids or three-componentretention aids. For example, the nanocrystalline cellulose (NCC) and/orthe microfibrillated cellulose can be used as an anionic retention aid.

Step 4: employing the paper pulp to make paper.

Paper made by the above papermaking process has an ash retention ofabout 60% to about 95%, and a first-pass ash retention of about 55% toabout 90%. Note: conventional paper has an ash retention of about 45% toabout 90%, and a first-pass ash retention of about 40% to about 85%.

The paper made by the above papermaking process has a high ashretention. The reason may include one or more of the following:

(1) The microfibrillated cellulose made by the TEMPO catalytic oxidationmethod has a complex composition and contains both water-solublecellulose and water-insoluble cellulose. The water-insoluble cellulosehas many carboxyl groups, causing it to delaminate due to theelectrostatic repulsion. Thus, the fine filler particles and latexparticles easily incorporate into the inside of the water-insolublecelluloses.

(2) The temperature of the modified filler composition is higher thanT_(g) of the latex, so the latex demulsify; the demulsified latex actsas a binder or a media for coupling the microfibrillated cellulose andthe filler together.

(3) Some of the water-soluble cellulose adsorbs the filler particles,which improves the dispersion ability of the filler, so the fillerdisperses uniformly in the modified filler composition. In case that themodified filler composition is kept static in a container for about 4hours, there will be no or few filler particles at the bottom of thecontainer.

(4) The surface of the filler particles adsorbs some of thewater-soluble cellulose, improving the chemical reactivity of thefiller. Thus, the filler with reactive functional groups chemicallybonds with the pulp fiber.

The disclosure provides a modified filler composition containing latex,the latex having a low glass transition temperature. The latex acts as abinder for coupling the microfibrillated cellulose and filler together,which makes the filler particles uniformly distribute on the surface ofthe microfibrillated cellulose. The paper pulp added with the modifiedfiller composition has a high filler retention. Thus, paper made by thepaper pulp has a high ash retention.

EXAMPLE 1

In this embodiment, the modified filler composition was prepared by thefollowing steps: (a) providing a microfibrillated cellulose aqueousdispersion containing 2 g of microfibrillated cellulose by dry weight;(b) adding 20 g of filler (GCC) to the microfibrillated celluloseaqueous dispersion, more than 95% of the filler by weight having aparticle size of less than 2 μm; (c) adding 0.2 g of styrene-butadienelatex having a T_(g) of about 10° C. to the microfibrillated celluloseaqueous dispersion to obtain a mixture; (d) stirring the mixture at atemperature of about 50° C. for about 5 minutes, thereby making themodified filler composition. A scanning electron micrograph of themodified filler composition is shown in FIG. 1.

COMPARATIVE EXAMPLE 1

A comparative filler composition was made by mixing microfibrillatedcellulose and filler together by stirring at about 600 RPM for about 5minutes, wherein the weight of the filler is 10 times the dry weight ofthe microfibrillated cellulose. The filler is uniformly dispersed GCC,and more than 95% of the filler by weight has a particle size of lessthan 2 μm. A scanning electron micrograph of the comparative fillercomposition is shown in FIG. 2.

FIG. 2 shows obvious aggregation of the filler particles on the surfaceof the microfibrillated cellulose, while FIG. 1 shows that the fillerparticles distribute much more uniformly on the microfibrillatedcellulose, with little aggregation.

The fillers in Example 1 and Comparative Example 1 were tested, and thetest results are listed in Table 1 below. The test results demonstratethat the filler in Example 1 has a much more uniform particle size.Note: the particle size uniformity is a value calculated by dividing thestandard deviation of the particle diameter by the mean particle size.

TABLE 1 Test type Comparative Example 1 Example 1 particle sizeuniformity of 11.9 7.42 filler Average particle size of 4.5 μm 3.9 μmfiller

EXAMPLE 2

The above modified filler composition in Example 1 containing 2 g ofmicrofibrillated cellulose and 20 g of filler was added into a LeafBleached Kraft Pulp (LBKP) having a dry weight of about 10 g; 2 g ofstarch was added into the above pulp; the pulp was diluted and employedto make paper.

COMPARATIVE EXAMPLE 2

20 g of filler were added into a LBKP having a dry weight of about 10 g;2 g of starch were added into the above pulp; the pulp was diluted andemployed to make comparative paper.

The papers made in Example 2 and Comparative Example 2 were tested, andthe test results are listed in Table 2 below. The test results show thatthe ash retention and the first-pass ash retention of the paper inExample 2 are much higher than those of the paper in Comparative Example2.

TABLE 2 Test type Comparative Example 2 Example 2 Basis weight g/m² 72.373.1 Thickness μm 94.7 85.7 Paper bulk cc/g 1.31 1.17 Air permeability s10.5 33.5 Fold endurance test, number 3 4 of folds (1.0 kg) Burstingindex kPa · m²/g 0.84 0.99 Tensile index N · m/g 17.4 21.8 Cohesion kg ·cm 0.53 0.99 Ash content % 45.74 51.4 First-pass ash retention % 42.163.3 ash retention 68.7 82.2

EXAMPLE 3

In this embodiment, the modified filler composition was prepared by thefollowing steps: (a) providing a filler suspension containing 2 g offiller (calcium carbonate) by weight; (b) adding microfibrillatedcellulose having a dry weight of 0.002 g into the filler suspension; (c)adding 0.002 g of styrene-butadiene latex having a T_(g) of less than10° C. into the filler suspension to obtain a mixture; (d) stirring themixture at a temperature of about 50° C. for about 5 minutes, therebymaking the modified filler composition.

A mixed pulp containing 10 g of Needle Bleached Kraft Pulp (NBKP) by dryweight and 10 g of alkaline peroxide mechanical pulp (APMP) by dryweight was provided. The above modified filler composition in Example 3was added into the mixed pulp; 0.08 g of starch was added into the abovemixed pulp; the mixed pulp was diluted to a concentration of about 0.3%and employed to make paper.

COMPARATIVE EXAMPLE 3

A mixed pulp containing 10 g of NBKP by dry weight and 10 g of APMP bydry weight was provided and adjusted to a concentration of about 4%.Then, 2 g of filler (calcium carbonate) and 0.08 g of cationic starchwas added into the mixed pulp; the mixed pulp was diluted to aconcentration of about 0.3% and employed to make comparative paper.

EXAMPLE 4

In this embodiment, the modified filler composition was prepared by thefollowing steps: (a) providing a filler suspension containing 5 g offiller (calcium carbonate) by weight; (b) adding microfibrillatedcellulose having a dry weight of 0.005 g into the filler suspension; (c)adding 0.005 g of styrene-butadiene latex having a T_(g) less than 10°C., and 0.005 g of a cross-linking agent (borax) into the fillersuspension to obtain a mixture; (d) stirring the mixture at atemperature of about 50° C. for about 5 minutes, thereby making themodified filler composition.

A mixed pulp containing 10 g of NBKP by dry weight and 10 g of APMP bydry weight was provided and adjusted to a concentration of about 4%. Theabove modified filler composition in Example 4 was added into the mixedpulp; 0.08 g of starch was added into the above mixed pulp; the mixedpulp was diluted to a concentration of about 0.3% and employed to makecomparative paper.

COMPARATIVE EXAMPLE 4

A mixed pulp containing 10 g of NBKP by dry weight and 10 g of APMP bydry weight was provided and adjusted to a concentration of about 4%.Then, 5 g of filler (calcium carbonate) and 0.08 g of cationic starchwere added into the mixed pulp; the mixed pulp was diluted to aconcentration of about 0.3% and employed to make paper.

The papers made in examples 3, Example 4, comparative example 3, andComparative Example 4 were tested, and the test results are listed inTable 3 below. Compared with the paper in comparative example 3, the ashretention and the first-pass ash retention of the paper in example 3 aresignificantly improved. Compared with the paper in comparative example4, the ash retention and the first-pass ash retention of the paper inExample 4 are also significantly improved.

TABLE 3 Comparative Comparative Test type Example 3 Example 3 Example 4Example 4 Basis weight g/m² 76.1 74.7 81.5 77.6 Thickness μm 184.5 179.4184.2 190.8 Paper bulk cc/g 2.42 2.40 2.26 2.46 Air permeability s 4.13.5 4.1 4.0 Fold endurance test, 59 92 40 62 number of folds (1.0 kg)Bursting index 2.38 2.53 2.22 2.28 kPa · m²/g Tensile index 43.8 46.140.0 42.1 N · m/g Cohesion kg · cm 0.97 1.02 0.85 0.92 Ash content %3.86% 5.49% 9.94% 12.54%  First-pass ash 40.1% 58.1% 55.2% 71.7%retention % ash retention % 42.5% 60.4% 59.6% 75.2%

EXAMPLE 5

In this embodiment, the modified filler composition was prepared by thefollowing steps: (a) providing a filler suspension containing 60 g offiller (calcium carbonate) by weight; (b) adding microfibrillatedcellulose having a dry weight of 4 g into the filler suspension; (c)adding 9 g of styrene-butadiene latex having a T_(g) less than 10° C.into the filler suspension to obtain a mixture; (d) stirring the mixtureat a temperature of about 50° C. for about 5 minutes, thereby making themodified filler composition.

A mixed pulp containing 10 g of NBKP by dry weight and 6 g of APMP bydry weight was provided and adjusted to a concentration of about 4%. Theabove modified filler composition in Example 5 containing 60 g of fillerand 4 g of microfibrillated cellulose were added into the mixed pulp;0.4 g of cationic starch was added into the above mixed pulp; the mixedpulp was diluted to a concentration of about 1%; a three-componentretention aid containing 300 PPM cationic polyacrylamide, 3600 PPMbentonite, and 800 PPM anionic polyacrylamide was added into the mixedpulp, the pulp being employed to make paper.

COMPARATIVE EXAMPLE 5

A mixed pulp containing 10 g of NBKP by dry weight, 6 g of APMP by dryweight, and 4 g of microfibrillated cellulose by dry weight was providedand adjusted to a concentration of about 4%. Then, 60 g of filler(calcium carbonate) and 0.4 g of cationic starch were added into themixed pulp; the mixed pulp was diluted to a concentration of about 1%; athree-component retention aid containing 300 PPM cationicpolyacrylamide, 3600 PPM bentonite, and 800 PPM anionic polyacrylamidewas added into the mixed pulp, the pulp being employed to makecomparative paper.

The papers made in Example 5 and Comparative Examples 5 were tested, andthe test results are listed in Table 4 below. Compared with the papermade in Comparative Example 5, the ash retention and the first-pass ashretention of the paper in Example 5 are significantly improved, and thenumber of folds, tensile index, and cohesion of the paper made inExample 5 also improved.

TABLE 4 Test type Comparative Example 5 Example 5 Basis weight g/m²107.9 112.0 Thickness μm 134.9 72.0 Paper bulk cc/g 1.25 0.64 Foldendurance test, number 2 11 of folds (1.0 kg) Air permeability s 18.951.4 Tensile index N · m/g 7.2 16.6 Cohesion kg · cm 0.64 2.25 Ashcontent % 59.6 62.4 First-pass ash retention % 49.2 84.0 ash retention %79.5 95.5

It is believed that the exemplary embodiments and their advantages willbe understood from the foregoing description, and it will be apparentthat various changes may be made thereto without departing from thespirit and scope of the disclosure or sacrificing all of its advantages,the examples hereinbefore described merely being preferred or exemplaryembodiments of the disclosure.

1. A modified filler composition, comprising: microfibrillatedcellulose, filler, and latex having a glass transition temperature ofless than 20° C., wherein the dry weight of the microfibrillatedcellulose is about 0.1% to about 10% of that of the filler, the dryweight of the latex is about 0.1% to about 15% of that of the filler. 2.The modified filler composition as claimed in claim 1, wherein themicrofibrillated cellulose has negative charge and comprises carboxylgroups, the content of carboxyl groups of the microfibrillated celluloseis in the range from about 0.06 to about 1.7 mmol/g.
 3. The modifiedfiller composition as claimed in claim 2, wherein the microfibrillatedcellulose comprises water-soluble cellulose having a mass percentage ofabout 0.1% to about 50% and water-insoluble cellulose having a masspercentage of about 10% to about 99.9%.
 4. The modified fillercomposition as claimed in claim 3, wherein the water-soluble cellulosescomprises nanocrystalline cellulose, nanofibrillated cellulose, andoligosaccharide.
 5. The modified filler composition as claimed in claim1, wherein the latex has a glass transition temperature of less than 10°C.
 6. The modified filler composition as claimed in claim 1, wherein thelatex is selected from the group consisting of polybutadiene latex,styrene-butadiene latex, carboxylic butadiene-styrene latex, cationicbutadiene-styrene latex, polyvinyl acetate latex, and any combinationthereof.
 7. The modified filler composition as claimed in claim 1,wherein the filler adsorbing on the surface of the microfibrillatedcellulose has a size uniformity of less than
 10. 8. The modified fillercomposition as claimed in claim 1, wherein more than 50% of the fillerhas a particle diameter of less than or equal to 2 μm.
 9. The modifiedfiller composition as claimed in claim 1, wherein the modified fillercomposition further comprises a cross-linking agent.
 10. The modifiedfiller composition as claimed in claim 9, wherein the cross-linkingagent is borate, borax, glutaric dialdehyde, or oxaldehyde; the dryweight of the cross-linking agent is about 0.1% to about 15% of that ofthe latex.
 11. A papermaking process, comprising: providing a modifiedfiller composition, the modified filler composition comprisingmicrofibrillated cellulose, filler, and latex having a glass transitiontemperature of less than 20° C., the dry weight of the microfibrillatedcellulose being about 0.1% to about 10% of that of the filler, the dryweight of the latex being about 0.1% to about 15% of that of the filler.providing a paper pulp; adding the modified filler composition into thepaper pulp; employing the paper pulp to make paper.
 12. The papermakingprocess as claimed in claim 11, wherein the modified filler compositionis prepared by mixing the microfibrillated cellulose, filler, and latextogether.
 13. The papermaking process as claimed in claim 11, whereinthe process further comprises a step of adding unmodified filler to thepaper pulp prior to employing the paper pulp to make paper.
 14. Thepapermaking process as claimed in claim 13, wherein the total weight ofthe filler in the modified filler composition and the unmodified fillerin paper pulp is about 10% to about 300% of the dry weight of the pulpfiber, the weight of filler in the modified filler composition is about80% to about 100% of the total weight of the filler in the modifiedfiller composition and the unmodified filler.
 15. The papermakingprocess as claimed in claim 11, wherein the microfibrillated cellulosehas negative charge and comprises carboxyl groups, the content ofcarboxyl groups of the microfibrillated cellulose is in the range fromabout 0.06 to about 1.7 mmol/g.
 16. The papermaking process as claimedin claim 11, wherein the microfibrillated cellulose compriseswater-soluble cellulose having a mass percentage of about 0.1% to about50% and water-insoluble cellulose having a mass percentage of about 10%to about 99.9%, the water-soluble celluloses comprises nanocrystallinecellulose, nanofibrillated cellulose, and oligosaccharide.
 17. Thepapermaking process as claimed in claim 11, wherein the latex has aglass transition temperature of less than 10° C.
 18. The papermakingprocess as claimed in claim 11, wherein the latex is selected from thegroup consisting of polybutadiene latex, styrene-butadiene latex,carboxylic butadiene-styrene latex, cationic butadiene-styrene latex,polyvinyl acetate latex, and any combination thereof.
 19. Thepapermaking process as claimed in claim 11, wherein the filler adsorbedon the surface of the microfibrillated cellulose has a size uniformityof less than
 10. 20. The papermaking process as claimed in claim 11,wherein more than 50% of the filler has a particle diameter of less thanor equal to 2 μm.
 21. The papermaking process as claimed in claim 11,wherein the modified filler composition further comprises across-linking agent, the cross-linking agent is borate, borax, glutaricdialdehyde, or oxaldehyde; the weight of the cross-linking agent is 0.1%to 15% of that of the latex.
 22. The papermaking process as claimed inclaim 11, wherein the process further comprises a step of addingauxiliary additive to the paper pulp prior to employing the paper pulpto make paper.